1. Field of the Invention
The present invention relates to a method and an apparatus for the quantitative determination of the concentration of optically active substances, particularly glucose, in the body fluid of a patient, by polarimetry. The quantity of optically active substances is determined by a comparison signal, such as a difference or quotient signal. The present invention includes a first light source with which a first linear polarized light beam is generated that transilluminates the substance to be analyzed and charges a detector via an analyzer.
2. Description of the Invention
German Published Application 29 44 113 and EP-A 0 030 610 disclose methods and apparatus for the quantitative determination of optically active substances by polarimetry. In these methods, the specimen of the optically active substance is illuminated with linearly polarized light that has passed through a Faraday modulator. After the light. has passed through the modulator, the light ray is divided into a measurement ray and a reference ray, both of which are detected separately by a detector, whereby a quotient or difference signal is formed from the signals obtained by the detector, this quotient or difference signal being utilized for the quantitative determination of an optically active substance in the transilluminated specimen.
The apparatus of this method has a complicated optical structure that is considerably expensive to miniaturize. The method of the prior art utilizes a Faraday modulator whose means for generating a magnetic field has a high power consumption, and thus, only enables short local mode operating in vivo.